1. Field of the Invention
The present invention relates to an ink jet recording head and an ink jet recorder, and more particularly to an ink jet recording head for discharging ink supplied from an ink chamber having an air layer therein, and an ink jet recorder which evacuates air from the ink chamber of the recording head by vacuum suction.
2. Description of the Prior Art
A prior art recording head of an ink jet recorder has a common ink chamber for a plurality of nozzles. The ink chamber is moved with the head as a carriage moves. In order to relieve the impact due to reversal of the direction of movement of the carriage, the ink chamber is provided with an air layer which absorbs a momentary rise in ink pressure in the nozzle at the time of the carriage return and minimizes pressure applied to the nozzle. The quantity of the air layer required for such buffering function is usually 0.1-0.3 cc. In order to keep the volume of the air layer constant the prior art head requires air evacuation means as shown in FIGS. 1 and 2.
In FIG. 1, a head 1 having a plurality of nozzles arranged in a line is mounted on a carriage 2, which is reciprocally movable on a shaft 3. The recording head 1 has an ink chamber for supplying ink to nozzles. Ink 6 is supplied to the ink chamber through an ink supply pipe 4. An air layer 7 is formed in the head 1. In order to form the air layer 7 on the ink 6, that is, in order to keep the volume of the air layer constant, an air evacuation tube 5 is connected to air evacuation means and is movable with the carriage. Since the tube is a flexible plastic tube, the ink is readily vaporized. Further, since the tube is moved, the arrangement is complex.
In another air evacuation method, a vent valve 8 is used as shown in FIG. 2. The vent valve 8 normally seals the air layer 7 and the ink 6 by a stationary seal member 9. If vaporization of the ink increases the volume of the air layer, the vent valve 8 is pushed in the direction of the arrow, shown in FIG. 2, against the biasing force of a spring 8b so that the ink level is raised and the air is evacuated through a vent hole 8a. In this structure, however, it is very difficult to visually watch the ink level and there is a risk of contamination by leakage of the ink.